Krieghbaum, H. (1969). An Investment in Knowledge: The first dozen years of the National Science Foundation's summer institutes programs to improve secondary shool science and mathematics teaching, 1954-1965. Univ.Pr..
শিকাগো স্টাইল (17 তম সংস্করণ) উদ্ধৃতিKrieghbaum, Hillier. An Investment in Knowledge: The First Dozen Years of the National Science Foundation's Summer Institutes Programs to Improve Secondary Shool Science and Mathematics Teaching, 1954-1965. NewYork: Univ.Pr., 1969.
M.L.A (9 ম সংস্করণ) উদ্ধৃতিKrieghbaum, Hillier. An Investment in Knowledge: The First Dozen Years of the National Science Foundation's Summer Institutes Programs to Improve Secondary Shool Science and Mathematics Teaching, 1954-1965. Univ.Pr., 1969.
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